#4. Mark Zuckerberg – Palo Alto, California

The youngest richest entrepreneur docks most of his wealth in schools, health and other philanthropies. His real estate portfolio include his home in Palo Alto and a 9.9-million pied-a-terre near Dolores Park in San Francisco. Mr. Zuckerberg purchased his first Craftsman-style 5,000-square-foot home in Palo Alto in 2011 for $7 million. He snapped up four of the houses surrounding his home in the following years for about $43.8 million to better keep his privacy. But his plan to tear down and rebuild those four homes has been stalled.